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Monday, November 26, 2007

The Digital Lens Revisited

In a world of marketing buzzwords like 'optimized' and 'designed for digital,' what's really going on behind all the hype?

This Article Features Photo Zoom

digital lens revisitedBefore plunking down a credit card to purchase a new lens, I think all of us want to know we're making a good decision. Is this really the best lens for my camera and the type of work I want to do? Or can I use one I already have, even if the lens isn't specifically designed for digital capture?

Because of the physical variations between film and digital image sensors, there's a need for specialized optics, especially if you're using a D-SLR with a sub-full-frame sensor. Cameras in this category include all Nikon D-SLRs except the new D3, the Canon EOS 40D and EOS 30D, the Sigma SD14, the Fujifilm S5 Pro and IS Pro, the Sony Alphas and all Olympus D-SLRs, to name a few.

the digital lens revisited With full-frame, 24x36mm sensors or larger digital-back chips, the need for specialized optics may not be as pronounced, depending on the lens and the camera, but it's still there. The fact that we're seeing an ever-increasing number of lenses being made with digital capture in mind isn't a superfluous phenomenon.

Steve Heiner, Senior Technical Manager for Nikon, describes the effort this way, “The majority of digital SLR designs in the market today utilize an imaging sensor that's roughly two-thirds the size of what's often referred to as a “full-sized” imaging sensor, or 24x36mm—the FX format for the Nikon D3. Because of this, and as an optical-lens manufacturer, Nikon set out to create a line of lenses designed specifically for its DX-format-size imaging sensor. The goal was to achieve a good balance between miniaturization in size and improvement in performance. By limiting use of these DX Nikkors to DX-format digital SLR cameras only, it's possible to create unprecedented lenses by making the most of their specific characteristics, while delivering a more compact lens with higher performance. This was the starting point for the development of the DX Nikkor series.”

figure 1 Canon's Chuck Westfall says it isn't necessarily a problem to use a lens that was originally designed for a film camera on a digital camera. “Generally speaking, you don't get any degradation just because you're using it on a digital camera compared to using it with film,” says Westfall. “It really depends on the lens and the camera.

“That said, all Canon EF lenses announced since 1999 feature modifications in design that improve their performance with digital SLRs without affecting their performance with 35mm SLRs.”

As of 2001, Sigma has upgraded its entire line of lenses, even the full-frame lenses, to be better suited to the digital format. Says Sigma's Tom Sobey, “The DG type that are for both film and digital, and the digital-only DC lenses for smaller sensors, all have the new DG coatings to improve contrast and minimize issues with ghosting and flare.”


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